1. Field of the Invention
This invention relates to manufacturing processes controlled by electronic processing and, in particular, to manufacturing processes involving adjustment for processing variables.
2. Art Background
A wide variety of manufacturing processes are controlled by electronic data processors such as computers. In such procedures a physical operation such as positioning is controlled by electrical signals that emanate from the data processor and that control processing through expedients such as positioners and/or directors. Exemplary of such processes is electron beam exposure equipment utilized in the fabrication of lithographic masks or integrated circuits where the electron beam is controlled by electric field directors. In such procedures, a chromium covered glass substrate or a device substrate overlain by an electron sensitive material is exposed by irradiation with an electron beam selectively by direction of the electron beam to impact the material in a desired pattern.
After exposure either the irradiated or nonirradiated portions of the electron sensitive material are removed typically through differential solvation processes to uncover in the desired pattern underlying regions of chromium or of the device. The longer the time the beam remains directed to impact a specific point the greater the difference in solvation characteristics between exposed and unexposed regions. The uncovered chromium or device region is then treated by procedures such as etching or metallization. For example, in producing a mask the uncovered chromium is removed to yield transparent regions in a pattern corresponding to that formed in the electron sensitive material. This transparent pattern is then used for photolithographic purposes in the manufacturing of devices such as integrated circuits.
In such processes, steps such as positioning must be adjusted to reflect the variables associated with the article being fabricated. In the example given above, such adjustment emanates from the scattering of impacting electrons off the underlying substrate. Such scattering of electrons produces a secondary exposure in regions adjacent to the areas of initial impact of the electron beam, thus causing a differential solubility between adjacent regions where none is desired or the same solubility where a difference is required.
Adjustment for such effects, especially in complicated systems such as those involved in lithography mask fabrication, requires excessive, uneconomic calculations. For example, in the context of photolithographic mask fabrication there are proposed algorithms such as described by M. Parikh in J. Vac. Sci. Technol., Vol. 15, pp. 931 (1978) for correcting inaccuracies associated with electron scattering. These methods involve inversion of large matrices to find the solutions, and would require years of computer time for a complex pattern. The time and expense associated with extensive calculation precludes such adjustment. Clearly, any improvement which allows adjustment and the associated article improvement with reasonable speed and cost is quite desirable.